Broadly speaking there are two types of users of network resources in the mobile domain. The first type of user is a so-called “contract” subscriber, for whom usage of network resources is paid for after the resources have used; typically the payment period is monthly. Such post paid systems might include a credit limit service where a user or other party such as parent and/or operator sets a limit of money to be allocated to services. The allocation can be also periodic and can for example specify an amount of services per month.
The second type of user is a so-called “pay as you go” subscriber, for whom usage of network resources is paid for prior to the provisioning of a given service. These services might include also credit limit type of functionality so as to prevent usage of all the credits in less than a predetermined time period.
Usage of network resources by either type of user can be sponsored by third parties by means of information content such as advertisements and the like. In this scenario all or part of the usage is offset by the third party, either directly or indirectly and, depending on the type of user, either before or after a given service has been provided.
One problem commonly experienced by the pay as you go user and by a post paid user when a predetermined credit limit is reached is the refusal or termination of a service when the pre-paid quota (or credit limit or advertisement sponsoring of related services) is lower than a predetermined threshold. As is commonly known, in such situations the network alerts the user of the imminent ending of the communications session by means of a message such as beep sound or voice message. This message is typically delivered to the user about 3 minutes before the quota or credit has expired; once the credit has expired the user is typically unable to make phone calls or use messaging or other services.
Several workers have proposed a solution to this problem, generally referred to as the “call me” service, whereby the user with no or a low amount of credit sends a message to the remote party with whom they wish to communicate, asking the remote party to call them. Such messages can be transmitted using the Unstructured Supplementary Services Data (USSD) or via the Short Messaging Service (SMS), as described in US patent application having publication number US2004/0192359. However, a problem with these methods is that the user needs to have some credit for the “call me” message to be transmitted through the network.